Epsom salt, also known as magnesium sulphate, is a mineral your body needs to function. Epsom salt is taken orally as a laxative and to treat magnesium deficiency. Intravenously, it's used to stop premature labour, prevent cerebral palsy in neonates and treat acute asthmatic episodes. Epsom salt mixed with bath water can help soothe itchy lesions, especially those due to herpes infection. Epsom salt is generally safe and well tolerated, but there are certain people for whom it may be dangerous.
People with kidney disease are more likely than others to develop hypermagnesemia. Hypermagnesemia is a condition in which too much magnesium accumulates in the bloodstream. Healthy kidneys can reduce tubular reabsorption to almost nothing to get rid of excess magnesium quickly. Damaged or failing kidneys can't excrete magnesium as effectively. This makes hypermagnesemia more likely, even with therapeutic dosing. Hypermagnesemia can cause muscle weakness, flaccid paralysis, low blood pressure and cardiac arrest. Treatment consists of dialysis and supportive care.
Epsom salt acts as a vasodilator. Vasodilators relax the muscles in the walls of blood vessels, causing them to widen. This can cause a steep drop in blood pressure. As blood pressure drops, the heart has to work harder to keep the body functioning. Unhealthy hearts may not be able to handle the stress. Arrhythmias and cardiac arrest can result. Epsom salt is indicated for very specific cardiac problems, but it is carefully monitored by a physician in these cases.
Magnesium and calcium are competing minerals. Magnesium can block some calcium from getting absorbed. This can be dangerous in people who are already suffer from hypocalcaemia, as magnesium can make the condition more severe. Severe hypocalcaemia typically presents with seizures, muscle spasms, congestive heart failure and tetany. Hypocalcaemia is treated with intravenous calcium and vitamin D.
People with appendicitis or signs of appendicitis should not take Epsom salt orally. The most common signs of appendicitis are right lower quadrant abdominal pain, nausea, vomiting and low-grade fever. Epsom salt draws water into the intestines and may cause intestinal muscles to contract. This combination can cause an inflamed appendix to rupture, leading to peritonitis. Peritonitis is life threatening and requires immediate surgical intervention.